I have heard that it is mentioned somewhere in the
Talmud that in the future, pork will no longer be trefah - unkosher.
I find this hard to believe! Is there anything you can find
to back this up?

Dear Dvora,

The Sages say, "Why is a pig called 'chazir?'
Because it is destined to 'chazor' - return - to a state of
purity." It's not clear if this is literal or allegorical.
Either way, the idea is this: Everything, even evil, is ultimately
rooted in holiness. The good is merely hidden and covered up.
In the future, when Hashem "slaughters the evil inclination,"
evil will vanish and everything's inherent good will be revealed.
Even pig, representing everything "not kosher," will
find its proper place.